Compressor



E. GAUS COMPRESSOR Filed DSG. 27, 1965 AGENTS United States Patent O 3,325,085 COMPRESSOR Ernst Gaus, Freudenstaedter Strasse 1072, iEnzkloestel-le, Germany Filed Dec. 27, 1965, Ser. No. 516,339 Claims priority, application Germany, Mar. 29, 1965,

11 Claims. (Cl. 230-55) This invention relates to compressors, and particularly to compressors in which the reciprocating movements of a piston or plunger are energized by a spring-mounted solenoid coil oscillating in the air gap of a magnetic circuit when passed by alternating current.

Compressors of the general type described have few movable parts, are relatively simple, and occupy little space. They have been used in domestic refrigerators for compressing a refrigerant medium such as a fluorinated hydrocarbon. The known compressors depend for operativeness on tight sealing engagement between the piston or plunger and a cooperating cylinder. The compressors operate effectively only when the natural frequency of the plunger equals the frequency of the exciting alternating current. The resulting need for free movement of the piston or plunger makes it difficult to guide the latter effectively relative to the cylinder in the known devices, and the angular misalignment of piston and cylinder axis causes wear and leakage.

The primary object of the invention is the provision of a compressor of the type described which does not develop leaks along the interface of piston or plunger and cylinder due to angular misalignment and the resulting wear.

A more specific object of the invention is the provision of a compressor in which the cylinder part tends to align itself with the piston or plunger even if the path of the latter shifts.

Another object is the provision of a compressor in which the friction between plunger and cylinder is held to a minimum by a simple and effective pressure lubrication system.

A further object is the provision of a compressor in which the plunger is securely guided in the cylinder to ensure co-axiality of the cylinder with the path of the plunger, yet movements of the plunger transverse of the axis are not impeded `by the cylinder.

With these and other objects in view, the invention provides a casing divided by a partition into two compartments connected by an elongated aperture in the partition. A magnetic circuit assembly which defines an air gap between two pole pieces thereof is an essential element of the partition. A solenoid coil assembly has a part which is movably received in the air gap and oscillates in the direction of the longitudinal axis of the aforementioned aperture when alternating current passes through the coil. An axially elongated guide sleeve or cylinder is arranged in the aperture of the partition in such a manner that its outer face and the wall of the partition in the aperture define an axially elongated free space of annular `cross section about the axis in the aperture. An axial portion of the guide sleeve is fastened to the partition wall in such a manner that the remainder of the sleeve can move in a direction transverse of the axis.

The two axial ends of the annular free space are sealed. A plunger is attached to the coil assembly for axial oscillating movement therewith, and a portion of the plunger is received in the guide sleeve in sealing movable engagement. Valves are provided in the manner customary in piston pumps for admitting fluid from one of the compartments in the casing to the sleeve or cylinder when the plunger moves axially in the sleeve in a direction inward of said one compartment, and for admitting the ICC fluid from the sleeve to the other compartment when the plunger moves in the opposite direction.

The coil assembly essentially consists of a carrier, springs which secure the carrier to the casing for axial oscillation in one of the compartments, and a conductive winding which is received in the air gap of the magnetic circuit. The aperture is formed in one of the pole pieces, and the length of the `sleeve should not be substantially smaller than tive times its average dimension perpendicular to the length.

When the free space between the sleeve and the internal wall of the partition communicates with a source of lubricant under pressure, radial passages through the guide sleeve aligned with the plunger portion received in the sleeve give the lubricant access to the sealingly engaged surfaces of the guide sleeve and of the plunger.

Other features and many of the attendant advantages of this invention will be readily apparent from the following detailed description of a preferred embodiment when considered with the attached drawing in which the sole figure shows a compressor of the invention in elevational section.

The outer casing of the compressor consists of a cast aluminum alloy rich in silicon and has an upper portion 1 having the approximate shape of a bell and a lower portion or cover 2 in the shape of a flanged cup. The casing is generally of circular cross section about an upright axis. A coil carrier 3 of insulating material is mounted in the `casing for axial oscillation between helical compression springs 4, 5. Insulated conductors 6, 7 connect a coil 8 lixedly mounted on the carrier 3 to a non-illustrated A.C. power line. The carrier 3 has the approximate shape of an inverted cup which encloses most of the spring 5 and from whose free rim the coil 8 coaxially depends.

A magnetic circuit is formed by an annular permanent magnet 9 and two pole pieces 10, 10' which define an annular gap 11 centered on the casing axis and movably receiving the coil 8. The magnet 9 is a ring of rectangular cross section and is axially Vinterposed between respective radial faces of the pole pieces 1t), lll. The latter are rings of L-shaped cross sections radially separated by the gap 11. The elements of the magnetic circuit constitute a partition which axially divides the cavity of the casing into a low pressure compartment 12 above the partition` and a high pressure compartment 13 under the partition.

An axially elongated plunger 14 is coaxially mounted on the coil carrier 3 and extends from the compartment 12 which encloses the carrier 3 into an axially elongated, central aperture 15 in the pole piece 10 toward the high pressure compartment 13. An axial bore 16 in the plunger is adapted to connect the two compartments, and is blocked by a check-valve 17 during the downward compression stroke of the plunger 14. Circumferential grooves 14 are axially `spaced on the outer face of the plunger.

A supply pipe 18 passing in sealing engagement through the cover 2 and the partition formed by the magnetic circuit has its orifice in the low-pressure compartment 12, and a discharge conduit 29 centrally set into the cover 2 communicates with the compartment 13.

The plunger 14 is guided in the aperture 15 by a sleeve 19 whose internal diameter is about one fifth of its axial length. The lower end of the sleeve 19 carries an integral collar 20 which is a press tit in the enlarged lower orifice of the aperture 15. The remainder of the sleeve 19 is thereby radially spaced from the walls of the aperture 15.

`A body of lubricant 21 in the bottom of the cup formed by the cover 2 receives the open end of a vertical lubricant tube 22 leading to a bore 23 in the pole piece 10" which communicates with the cylindrical space 19 between the sleeve 19 and the walls of the aperture 15. The interface between the sleeve 19 and the plunger 14 is connected to the space 19' by narrow radial bores 24 in the sleeve 19. The space 19 is axially sealed by the collar 20 o-f the sleeve 19 and by an O-ring 25 of resilient ma-` terial axially secured in a groove of the pole piece 10.

In order to hold friction of the plunger 14 in the sleeve 19 to a minimum, the plunger is made of alloy steel whereas the sleeve is made of a Zinc-bearing bronze.

The bottom end of the sleeve 19 is normally closed by a valve plate 26 under the pressure of a helical spring 27 which abuts against a central tubular boss 28 of the cover 2 in which the discharge conduit 29 is sealingly received.

The internal cross section of the bore 16 in the plunger 14 is circular and uniform from the upper orice of the bore inthe co-mpartment 13 to the check valve 17 whose closing member is a small plate limited in its axial movement downwardly away from an internal shoulder of the plunger 14 by a cross shaped member 30, fixedly mounted in the bore 16.

A compensating ring 31 is coaxially mounted in the compressor compartment 12 between two heavy helical compression springs 32, 33 which respectively abut against the upper casing portion 1 and the pole piece 10. Retaining rings 34, 35 of stepped cylindrical shape are set into the ring 31 and respectively engage the ends of the springs 32, 33 for centering the ring 31 in the casing. Annular wall portions 36, 37 of the bell 1 and of the pole piece 10 respectively locate the other ends of the springs 32, 33 in abutting engagement.

Current is supplied from the afore-mentioned conductor 6 to one terminal of the coil 8 by a pin plug 38 and a socket assembly 44 which includes a plastic member 39 having an annular shoulder 40 constituting an abutment for the spring 4. A spring metal blade 41 inserted in the member 39 is apertured to receive the terminal portion of the conical free end of the pin plug 38 and is partly exposed on the shoulder 40 for contact with the spring 4. A conductive connection is provided between the other end of the spring 4 and one terminal of the coil 8 by a heavy metallic abutment ring 42 on the coil carrier 3 and a wire 43 partly embedded in the carrier 3.

A pin plug 50 on the conductor 7 similarly engages an apertured spring blade 53 in a cavity 51 of a receptacle 52 mounted in aligned recesses of the pole piece 10 and the cover 2. The blade 53 is connected by a wire 56 with a metallic abutment ring 54 mounted on the radial top face of the pole piece 10', and insulated from the same by an interposed plastic ring 55. The abutment ring 54 is engaged by the spring under the resilient pressure of the latter. A contact ring 57 on the carrier 3 engaged by the spring 5 and a conductor 58 leading from the ring 57 to the other terminal of the coil 8 complete the electrical circuit of the latter. Locating recesses 60 in the' aforementioned top face of the pole piece are engaged by conforming integral projections of the plastic ring 55 to prevent rotation of latter, only one recess and projection being shown in the drawing.

Annular gaskets 61, 62 partly received in concentric circular grooves in the flange portion of the cover 2 engage the pole piece 10 for sealing the high-pressure compartment 13. The pole piece 10 is held in tight contact with the gaskets 61, 62 by an internal annular shoulder 63 on the bell-shaped upper casing portion 1 which abuttingly engages the pole piece 10. A spring ring 64 engages a groove in an exposed, cylindrically concave wall of the casing portion 1 to secure the axial position of the cover 2.

When the coil 8 is energized with alternating current, the coil oscillates axially in the air gap 11 between the pole pieces 10, 10. When the plunger 14 moves downward with the -coil 8, the valve 17 is closed, and fluid in the sleeve 19 under the plunger is compressed until ythe force of the spring 27 cannot hold the valve plate 26, and fluid under pressure is discharged into the high pressure compartment 13 for discharge through the conduit 29. During the upward suction stroke of the plunger 14, the valve plate 26 is closed and the check valve 17 is o-pen so that the space under the plunger 14 in the sleeve 19 fills with fluid admitted to the low-pressure compartment 12 through the supply pipe 18. The ring 31 oscillates simultaneously at the same frequency as the coil carrier 3 and associated elements, but 180 out of phase with the coil carrier if the springs 32, 33 and the mass of the ring 31 are properly selected. Vibrations transmitted to a non-illustrated supporting structure are minimal.

The clearance between the plunger 14 and the sleeve 19 can be made very small without any danger of jamming because the plunger is guided in the long sleeve over most of the length of the latter in all operative positions of the plunger. A clearance of 0.03 mm. is entirely practical, and leakage losses are negligible when the compressor is used with the fluorinated hydrocarbons commonly employed in refrigeration systems such as Freon 12 or Freon 22 (CF2C12 or CHF2C1).

Another factor which importantly contributes to the prevention of jamming or freezing of the plunger 14 in the sleeve 19 is the mounting of the latter in the pole piece 10 by its lower end whereas the sealing ring 25 permits the upper end of the somewhat resilient sleeve 19 to swing radially toward and away from the casing axis, or to move in an arc about the axis. The provision of a free space 19 between the sleeve 19 and the cylindrical wall of the aperture 15 is therefore an important feature of the invention.

It has the secondary advantage of providing a convenient path for lubricant to the interface between the sleeve 19 and the plunger 14. The wear of the cooperating faces of the sleeve and of the plunger is extremely small, and the compressor has a longer useful life than similar known compressors before its output is reduced to an unsatisfactory value by leakage from the high-pressure to the lowpressure compartment, and a greater pressure differential can be maintained between the compartments 12, 13.

Although the guided length of the plunger 14 in the sleeve 19 is greater than that of similar compressors known heretofore, the axial dimensions of the compressor of the invention are not increased.

The use of steel as a material of construction for the plunger 14 and of bronze in the sleeve 19 is preferred over the reversed arrangement which would provide the same low coefficient of friction. The higher coefficient of thermal expansion of the sleeve material prevents an increase in friction when the pump warms up during service, but the difference is not great enough to cause leakage. The sleeve 19 is free to expand thermally into the space 19', and the portion of the sleeve receiving the plunger 14 cannot be warped by expansion in a manner that would interfere with free movement of the plunger.

Lubricant is forced into the space 19 by the high pressure prevailing in the compartment 13. Admixture of lubricant to the discharged compressed fluid is held to a minimum by keeping the orifice of the discharge conduit 29 as close to the valve plate 26 and as far from the surface of the lubricant body 21 as possible. The stream of compressed fluid discharged about the valve plate 26 during the pressure stroke of the plunger 14 tends to keep lubricant droplets away from the orifice of the conduit 29.

The flow resistance of the bore 16 is very small because its cross section is uniform over most of its length. The selected type of check valve 17 has been found to offer particularly low resistance to the flow of fluid into the sleeve 19 during the suction stroke of the plunger 14. The dimensions of a compressor of the type illustrated are very small. The frictional resistance offered by the compressor to the fluid during the suction stroke therefore has a very significant influence on the capacity of the device.

The plunger 14 not only oscillates axially in the sleeve 19, but it also rotates with the carrier 3 and the coil 8 about the axis of the compressor. This rotation is due to minute and practically unavoidable deviations of the movable parts of the compressor from nominal design dimensions. The same deviations account for the aforementioned small oscillatory movements of the plunger in a direction transverse to the axis. The inherent rotary movement of the plunger causes the wear of the plunger and sleeve resulting from the transverse oscillations of the plunger which are not fully compensated by the resilient mounting of the sleeve to be distributed over the entire interface of plunger and sleeve, and thereby further reduces the effect of such wear on the useful life of the compressor.

Rotation of the coil carrier 3 about the axis of the compressor can be ensured in a known manner by winding the coil 8 so that the tangential components of the magnetic fields generated by current flowing in the several turns of the winding do not balance each other. The carrier 3 when provided with a suitable wound coil 8 performs an angular oscillating movement. The amplitude of the angular oscillating movement becomes quite large even with small tangential imbalance of the afore-mentioned magnetic fields if the natural frequency of the oscillating system is made to approximate the frequency of the alternating supply current by suitable choice of the springs 4, 5.

The frictional forces exerted by the springs 4, on the rotating carrier 3 vary with the axial displacement of the coil carrier 3 and the plunger 14. With properly selected springs 4, 5, the angular oscillations as well as the axial oscillations of the coil carrier 3 are synchronized with those of the exciting alternating current. When the angular momentum is sufficient to overcome the friction between the springs and the carrier 3 only when the axial contact pressure between springs and carrier is at a minimum, the carrier 3 rotates together with the plunger 14 in one direction at a speed which fluctuates at the frequency of the exciting current.

Tuning of the oscillating system may require adjustment of the combined effective mass of the carrier 3 and of associated elements. Such adjustment is readily accomplished by replacing the ring 42 by another ring of greater or smaller mass.

The ring 31 and the associated springs 32, 33, which jointly constitute a compensating oscillator, are also readily replaceable to permit proper selection by trial and error. A properly selected compensating oscillator suppresses the outward transmission of oscillations from the compressor to such an extent that the compressor may be supported entirely on the gas lines which supply low pressure fluid and carry the compressed fluid away. These gas lines are shown at 18 and 29 in the drawing. Turning of the compensating oscillator is facilitated by mounting the compressor on a spring supported table which is caused to oscillate when forces are transmitted thereto by the compressor.

It should be understood, of course, that the foregoing disclosure relates only to a preferred embodiment of the invention, and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. A compressor comprising, in combination:

(a) a casing enclosing a cavity;

(b) partition means dividing said cavity into two compartments and being formed with an aperture having an axis and axially connecting said compartments, said aperture being axially elongated, said partition means including magnetic circuit means defining a sap;

(c) coil means axially movable in said gap;

(d) conductor means for connecting said coil means to a source of alternating current, said coil means being responsive to flow of said current therethrough to oscillate axially in the gap of said magnetic circuit means;

(e) an axially elongated guide sleeve in said aperture, said guide sleeve having a radially outer face spaced from said partition means and defining therewith an axially elongated free space of annular cross section about said axis in said aperture;

(f) fastening means fastening an. axial portion of said sleeve to said partition means for movementof the remainder of the sleeve in a direction transverse of the axis;

(g) sealing means axially sealing the ends of said free space;

(h) plunger means secured to said coil means for axial oscillating movement therewith, a portion of said plunger means being received in said guide sleeve in sealing movable engagement; and

(i) valve means -for admitting fluid from one of said compartments to said sleeve in response to axial movement of said plunger means in the sleeve in one direction, and for admitting the fluid from said sleeve to the other compartment in response to axial movement of the plunger means in the opposite direction.

2. A compressor as set forth in claim 1, wherein said coil means include a carrier, spring means securing the carrier to the casing for axial oscillation in one of said compartments, and a conductive winding on the carrier, the winding being received in said gap, said magnetic circuit means including two pole pieces defining said gap therebetween, the gap extending about said axis, one of said pole pieces being formed with said aperture, the ratio of the axial length of said guide sleeve to the average internal dimension of the sleeve perpendicular to the length being not substantially smaller than 5 to 1.

3. A compressor as set forth in claim 1, wherein the coeiiicient of thermal expansion of said guide sleeve is greater than that of said portion of the plunger means.

4. A compressor as set forth in claim 1, wherein said fastening means include a collar on said guide sleeve in fixed engagement with said partition means in said aperture, said collar constituting an element of said sealing means.

5. A compressor as set forth in claim 1, further comprising a source of lubricant under pressure communicating with said free space, said guide sleeve being formed with a radial passage therethrough communicating with said free space and aligned with said portion of the plunger means for access of lubricant from said free space to the sealingly engaged surfaces of said guide sleeve and of said plunger means.

6. A compressor as set forth in claim 5, wherein said source includes `a receptacle communicating with said other compartment and adapted to hold a body of lubricant to a predetermined level and a conduit having respective orifices in said receptacle below said level in said free space.

7. A compressor as set forth in claim 1, wherein said plunger means includes a plunger member having an axial bore therethrough, said valve means including a first valve member mounted in said bore for movement toward a bore closing position in response to fluid ow from said other to said one compartment, a second valve member interposed between said guide sleeve and said other compartment, and yieldably resilient means biasing said second Valve member toward a closing position and responsive to a predetermined fluid pressure in said guide sleeve to permit movement of the second valve member away from said closing position thereof, said axial bore being open toward said one compartment, and the cross section thereof being uniform from said one compartment to said first valve member.

8. A compressor as set forth in claim 1, wherein said coil means include means responsive to said flow of current for rotating said plunger means in said guide sleeve about said axis.

9. A compressor as set forth in claim 1, further corr1 prising means for varying the effective mass of said coil means. i

10. A compressor as set forth in claim 1, wherein said coil means include a carrier, spring means securing the carrier to the casing for axial oscillation in one of said compartments, and a conductive winding on the carrier, the winding being received in said gap, the compressor further comprising a compensating oscillator in saidV one compartment, said oscillator including a ring member coaxially enveloping said carrier, a spring member interposed between said ring member and said casing, and another spring member interposed between said ring member and said partition means.

11. A compressor as set forth in claim 1, wherein said magnetic circuit means include two annular pole pieces coaxially arranged relative to said axis, respective portions of said pole pieces being radially spaced to define said gap therebetween, the gap being annular, the magnetic circuit means further including a magnet interposed between said pole pieces, the radially inner one of said pole pieces being centrally formed with said axially elongated aperture; said coil means including a carrier in one of said compartments, two spring members respectively axially interposed between said inner pole piece and the carrier, and said carrier and the casing, and an annular winding xedly fastened to said carrier and movably received in said gap, said plunger means being fastened to said carrier and extending therefrom into said guide sleeve; said fastening means including a collar on a longitudinally terminal portion of said guide sleeve remote from said carrier and xedly engaging said inner pole piece in said aperture, an annular sealing member of yieldably resilient material on a longitudinally terminal portion of said guide member Vadjacent said carrier engaging said inner pole piece, said collar and said sealing member jointly constituting said sealing means; said other compartment constituting a receptacle having a top portion and a bottom portion adapted to hold a body of liquid lubricant and a conduit having respective orifices in said bottom portion and in said free space, said guide sleeve being formed with a radial passage therethrough communicating with said free space and aligned with said portion of said plunger means for access of lubricant from said free space to the sealingly engaged surfaces of said guide sleeve and said plunger means.

References Cited UNITED STATES PATENTS ROBERT M. WALKER, Primary Examiner. 

1. A COMPRESSOR COMPRISING, IN COMBINATION: (A) A CASING ENCLOSING A CAVITY; (B) PARTITION MEANS DIVIDING SAID CAVITY INTO TWO COMPARTMENTS AND BEING FORMED WITH AN APERTURE HAVING AN AXIS AND AXIALLY CONNECTING SAID COMPARTMENTS, SAID APERTURE BEING AXIALLY ELONGATED, SAID PARTITION MEANS INCLUDING MAGNETIC CIRCUIT MEANS DEFINING A GAP; (C) COIL MEANS AXIALLY MOVABLE IN SAID GAP; (D) CONDUCTOR MEANS FOR CONNECTING SAID COIL MEANS TO A SOURCE OF ALTERNATING CURRENT, SAID COIL MEANS BEING RESPONSIVE TO FLOW OF SAID CURRENT THERETHROUGH TO OSCILLATE AXIALLY IN THE GAP OF SAID MAGNETIC CIRCUIT MEANS; (E) AN AXIALLY ELONGATED GUIDE SLEEVE IN SAID APERTURE, SAID GUIDE SLEEVE HAVING A RADIALLY OUTER FACE SPACED FROM SAID PARTITION MEANS AND DEFINING THEREWITH AN AXIALLY ELONGATED FREE SPACE OF ANNULAR CROSS SECTION ABOUT SAID AXIS IN SAID APERTURE; (F) FASTENING MEANS FASTENING AN AXIAL PORTION OF SAID SLEEVE TO SAID PARTITION MEANS FOR MOVEMENT OF THE REMAINDER OF THE SLEEVE IN A DIRECTION TRANSVERSE OF THE AXIS; (G) SEALING MEANS AXIALLY SEALING THE ENDS OF SAID FREE SPACE; (H) PLUNGER MEANS SECURED TO SAID COIL MEANS FOR AXIAL OSCILLATING MOVEMENT THEREWITH, A PORTION OF SAID PLUNGER MEANS BEING RECEIVED IN SAID GUIDE SLEEVE IN SEALING MOVABLE ENGAGEMENT; AND (I) VALVE MEANS FOR ADMITTING FLUID FROM ONE OF SAID COMPARTMENTS TO SAID SLEEVE IN RESPONSE TO AXIAL MOVEMENT OF SAID PLUNGER MEANS IN THE SLEEVE IN ONE DIRECTION, AND FOR ADMITTING THE FLUID FROM SAID SLEEVE TO THE OTHER COMPARTMENT IN RESPONSE TO AXIAL MOVEMENT OF THE PLUNGER MEANS IN THE OPPOSITE DIRECTION. 